High fidelity interactions between cavities, part 1

The long lifetime and large Hilbert space offered by bosonic modes in microwave cavities makes them excellent candidates for quantum memories. By engineering a beamsplitter interaction between these cavities, one can entangle and manipulate these memories. Implementations using 4-wave mixing provided by a driven transmon coupled to two cavities have been limited by other, undesired 4th order processes such as the AC Stark Shift. We mitigate this by replacing the transmon with a custom-made conversion element, diluting the 4th order nonlinearity of the conversion element while correspondingly driving it harder, and pumping the element further off-resonance. Achieving this requires careful engineering to deliver strong off-resonant pump tones without inducing unwanted radiative losses. Here, I will talk about the expected performance of such a device, and how we solve these engineering challenges.